Electronic devices with time domain radio-frequency exposure averaging

ABSTRACT

An electronic device may include a radio that generates a first maximum power based on a radio-frequency exposure (RFE) budget. The radio may transmit signals subject to the first maximum power during a subperiod of an averaging period and may generate an instantaneous RFE metric value based on an antenna coefficient and the conducted transmit power of the antenna during the subperiod. The radio may generate a consumed RFE value by averaging the instantaneous RFE metric value with previous instantaneous RFE values from the averaging period, may generate a remaining budget based on the consumed RFE value, may generate a second maximum transmit power based on the remaining budget, and may transmit signals during a subsequent subperiod subject to the second maximum power. Time-averaging the RFE metric may serve to optimize performance of the radio relative to scenarios where the radio performs time-averaging of conducted TX power.

FIELD

This disclosure relates generally to electronic devices and, moreparticularly, to electronic devices with wireless circuitry.

BACKGROUND

Electronic devices are often provided with wireless capabilities. Anelectronic device with wireless capabilities has wireless circuitry thatincludes one or more antennas. The antennas transmit radio-frequencysignals. During transmission, the radio-frequency signals are sometimesincident upon nearby external objects such as the body of a user oranother person.

Electronic devices with wireless capabilities are typically operated ingeographic regions that impose regulatory limits on the amount ofradio-frequency exposure produced by the electronic device intransmitting radio-frequency signals. It can be challenging to designelectronic devices that meet these regulatory limits without sacrificingan excessive amount of radio-frequency performance, particularly as thedevice transitions between a wide range of operating environments.

SUMMARY

An electronic device may include wireless circuitry controlled by one ormore processors. The wireless circuitry may include radios that transmitradio-frequency signals using at least one antenna. The radios mayinclude a first set of one or more radios that transmit radio-frequencysignals at frequencies less than 6 GHz. The radios may include a secondset of one or more radios that transmit radio-frequency signals atfrequencies greater than 6 GHz. The first set of radios may be subjectto a regulatory specific absorption rate (SAR) limit over a regulatoryaveraging period. The second set of radios may be subject to aregulatory maximum permissible exposure (MPE) limit over the regulatoryaveraging period.

The wireless circuitry may include a radio-frequency (RF) exposuremetric manager. The RF exposure metric manager may assign aradio-frequency exposure (RFE) budget (e.g., SAR and/or MPE budgets) toeach of the radios. Each radio may generate a first maximum transmitpower level based on its assigned RFE budget and an antenna coefficientassociated with an antenna used by the radio for transmission. Theantenna coefficient may also correspond to a combination of duty cycle,frequency band, radio-access technology, and device position. The radiomay transmit first radio-frequency signals during a first subperiod ofthe averaging period. The radio may generate an instantaneous RFE metricvalue based on the conducted transmit power of the radio and antennaduring the first subperiod and based on the antenna coefficient. Theradio may generate a consumed RFE metric value by averaging theinstantaneous RFE metric value with one or more instantaneous RFE metricvalues gathered during one or more prior subperiods of the averagingperiod. The radio may generate a remaining RFE budget based on theassigned RFE budget and the consumed RFE metric value. The radio maygenerate a second maximum transmit power level based on the remainingRFE budget and the antenna coefficient. The radio may transmit secondradio-frequency signals during a subsequent subperiod of the averagingperiod and subject to the second maximum transmit power level. Thisprocess may iterate to adjust maximum transmit power level over theaveraging period to ensure RFE compliance for the radio. Performingtime-averaging of the RFE metric may serve to optimize theradio-frequency performance of the radio relative to scenarios where theradio performs time-averaging of conducted TX power.

An aspect of the disclosure provides an electronic device. Theelectronic device can include an antenna. The electronic device caninclude a radio communicably coupled to the antenna. The electronicdevice can include one or more processors. The one or more processorscan be configured to generate a first maximum transmit power level basedon a radio-frequency exposure (RFE) budget assigned to the radio and anantenna coefficient associated with the antenna. The radio can beconfigured to transmit first radio-frequency signals using the antennaduring a first subperiod of an averaging period while subject to thefirst maximum transmit power level. The one or more processors can beconfigured to generate an instantaneous RFE metric value based on theantenna coefficient and a conducted transmit power of the antenna duringthe first subperiod. The one or more processors can be configured togenerate a consumed RFE metric value by averaging the instantaneous RFEmetric value with at least one additional instantaneous RFE metric valuegenerated by the one or more processors for one or more subperiods ofthe averaging period that are prior to the first subperiod. The one ormore processors can be configured to generate a remaining RFE budget forthe averaging period based on the consumed RFE metric value and the RFEbudget. The one or more processors can be configured to generate asecond maximum transmit power level based on the remaining RFE budgetand the antenna coefficient. The radio can be configured to use theantenna to transmit second radio-frequency signals during a secondsubperiod of the averaging period subsequent to the first subperiodwhile subject to the second maximum transmit power level.

An aspect of the disclosure provides a method of operating an electronicdevice having one or more antennas configured to handle one or moreradio-frequency polarizations, a radio subject to a limit onradio-frequency exposure (RFE) over an averaging period, and one or moreprocessors. The method can include with the radio, transmitting firstradio-frequency signals using the one or more antennas antenna during afirst subperiod of the averaging period while subject to a first maximumtransmit power level. The method can include with the one or moreprocessors, generating an instantaneous RFE metric value based on anantenna coefficient associated with the one or more antennas and basedon a conducted transmit power of the one or more antennas during thefirst subperiod. The method can include with the one or more processors,generating a consumed RFE metric value by averaging the instantaneousRFE metric value with at least one additional instantaneous RFE metricvalue generated for one or more subperiods of the averaging period thatare prior to the first subperiod. The method can include with the one ormore processors, generating a remaining RFE budget for the averagingperiod based on the consumed RFE metric value. The method can includewith the one or more processors, generating a second maximum transmitpower level based on the remaining RFE budget. The method can includewith the radio, transmitting second radio-frequency signals using atleast one of the one or more antennas during a second subperiod of theaveraging period while subject to the second maximum transmit powerlevel, the second subperiod being subsequent to the first subperiod.

An aspect of the disclosure provides an electronic device. Theelectronic device can include one or more antennas. The electronicdevice can include a radio communicably coupled to the one or moreantennas and subject to a limit on maximum permissible exposure (MPE)over an averaging period. The electronic device can include one or moreprocessors configured. The one or more processors can be configured toconvert an MPE budget assigned to the radio into a first maximumtransmit power level. The radio can be configured to transmit firstradio-frequency signals at a frequency greater than 6 GHz using at leastone of the one or more antennas during a subperiod of the averagingperiod and while subject to the first maximum transmit power level. Theone or more processors can be configured to generate an instantaneousMPE value based on a conducted transmit power of the one or moreantennas during the subperiod. The one or more processors can beconfigured to generate a consumed MPE value by averaging theinstantaneous MPE value with at least one prior instantaneous MPE metricvalue generated during the averaging period. The one or more processorscan be configured to generate a remaining MPE budget for the averagingperiod based on the consumed MPE value and the MPE budget. The one ormore processors can be configured to generate a second maximum transmitpower level based on the remaining MPE budget. The radio can beconfigured to transmit second radio-frequency signals at the frequencygreater than 6 GHz using at least one of the one or more antennas duringa subsequent subperiod of the averaging period and while subject to thesecond maximum transmit power level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an illustrative electronic device havingwireless circuitry with radios that transmit radio-frequency signalsaccording to radio-frequency exposure (RFE) metric budgets in accordancewith some embodiments.

FIG. 2 is a circuit block diagram of an illustrative radio havingcircuitry for managing RFE compliance subject to RFE budgets inaccordance with some embodiments.

FIG. 3 is a circuit block diagram of illustrative RFE budget conversioncircuitry in a radio in accordance with some embodiments.

FIG. 4 is a circuit block diagram of illustrative instantaneous RFEcalculation circuitry in a radio in accordance with some embodiments.

FIG. 5 is a flow chart of illustrative operations involved in using aradio to maintain RFE compliance by time averaging RFE metrics inaccordance with some embodiments.

FIGS. 6 and 7 are plots of power over time showing how time-averagingRFE metrics may optimize radio-frequency performance for a radio inaccordance with some embodiments.

DETAILED DESCRIPTION

Electronic device 10 of FIG. 1 may be a computing device such as alaptop computer, a desktop computer, a computer monitor containing anembedded computer, a tablet computer, a cellular telephone, a mediaplayer, or other handheld or portable electronic device, a smallerdevice such as a wristwatch device, a pendant device, a headphone orearpiece device, a device embedded in eyeglasses or other equipment wornon a user's head, or other wearable or miniature device, a television, acomputer display that does not contain an embedded computer, a gamingdevice, a navigation device, an embedded system such as a system inwhich electronic equipment with a display is mounted in a kiosk orautomobile, a wireless internet-connected voice-controlled speaker, ahome entertainment device, a remote control device, a gaming controller,a peripheral user input device, a wireless base station or access point,equipment that implements the functionality of two or more of thesedevices, or other electronic equipment.

As shown in the functional block diagram of FIG. 1, device 10 mayinclude components located on or within an electronic device housingsuch as housing 12. Housing 12, which may sometimes be referred to as acase, may be formed of plastic, glass, ceramics, fiber composites, metal(e.g., stainless steel, aluminum, metal alloys, etc.), other suitablematerials, or a combination of these materials. In some situations,parts or all of housing 12 may be formed from dielectric or otherlow-conductivity material (e.g., glass, ceramic, plastic, sapphire,etc.). In other situations, housing 12 or at least some of thestructures that make up housing 12 may be formed from metal elements.

Device 10 may include control circuitry 14. Control circuitry 14 mayinclude storage such as storage circuitry 16. Storage circuitry 16 mayinclude hard disk drive storage, nonvolatile memory (e.g., flash memoryor other electrically-programmable-read-only memory configured to form asolid-state drive), volatile memory (e.g., static or dynamicrandom-access-memory), etc. Storage circuitry 16 may include storagethat is integrated within device 10 and/or removable storage media.

Control circuitry 14 may include processing circuitry such as processingcircuitry 18. Processing circuitry 18 may be used to control theoperation of device 10. Processing circuitry 18 may include on one ormore processors, microprocessors, microcontrollers, digital signalprocessors, host processors, baseband processor integrated circuits,application specific integrated circuits, central processing units(CPUs), graphics processing units (GPUs), etc. Control circuitry 14 maybe configured to perform operations in device 10 using hardware (e.g.,dedicated hardware or circuitry), firmware, and/or software. Softwarecode for performing operations in device 10 may be stored on storagecircuitry 16 (e.g., storage circuitry 16 may include non-transitory(tangible) computer readable storage media that stores the softwarecode). The software code may sometimes be referred to as programinstructions, software, data, instructions, or code. Software codestored on storage circuitry 16 may be executed by processing circuitry18.

Control circuitry 14 may be used to run software on device 10 such assatellite navigation applications, internet browsing applications,voice-over-internet-protocol (VOIP) telephone call applications, emailapplications, media playback applications, operating system functions,etc. To support interactions with external equipment, control circuitry14 may be used in implementing communications protocols. Communicationsprotocols that may be implemented using control circuitry 14 includeinternet protocols, wireless local area network (WLAN) protocols (e.g.,IEEE 802.11 protocols—sometimes referred to as Wi-Fi®), protocols forother short-range wireless communications links such as the Bluetooth®protocol or other wireless personal area network (WPAN) protocols, IEEE802.11ad protocols (e.g., ultra-wideband protocols), cellular telephoneprotocols (e.g., 3G protocols, 4G (LTE) protocols, 3GPP Fifth Generation(5G) New Radio (NR) protocols, etc.), antenna diversity protocols,satellite navigation system protocols (e.g., global positioning system(GPS) protocols, global navigation satellite system (GLONASS) protocols,etc.), antenna-based spatial ranging protocols (e.g., radio detectionand ranging (RADAR) protocols or other desired range detection protocolsfor signals conveyed at millimeter and centimeter wave frequencies), orany other desired communications protocols. Each communications protocolmay be associated with a corresponding radio access technology (RAT)that specifies the physical connection methodology used in implementingthe protocol.

Device 10 may include input-output circuitry 20. Input-output circuitry20 may include input-output devices 22. Input-output devices 22 may beused to allow data to be supplied to device 10 and to allow data to beprovided from device 10 to external devices. Input-output devices 22 mayinclude user interface devices, data port devices, and otherinput-output components. For example, input-output devices 22 mayinclude touch sensors, displays (e.g., touch-sensitive and/orforce-sensitive displays), light-emitting components such as displayswithout touch sensor capabilities, buttons (mechanical, capacitive,optical, etc.), scrolling wheels, touch pads, key pads, keyboards,microphones, cameras, buttons, speakers, status indicators, audio jacksand other audio port components, digital data port devices, motionsensors (accelerometers, gyroscopes, and/or compasses that detectmotion), capacitance sensors, proximity sensors, magnetic sensors, forcesensors (e.g., force sensors coupled to a display to detect pressureapplied to the display), temperature sensors, etc. In someconfigurations, keyboards, headphones, displays, pointing devices suchas trackpads, mice, and joysticks, and other input-output devices may becoupled to device 10 using wired or wireless connections (e.g., some ofinput-output devices 22 may be peripherals that are coupled to a mainprocessing unit or other portion of device 10 via a wired or wirelesslink).

Input-output circuitry 20 may include wireless circuitry 24 to supportwireless communications and/or radio-based spatial ranging operations.Wireless circuitry 24 may include one or more antennas 34. Wirelesscircuitry 24 may also include n+1 radios 28 (e.g., a first radio 28-0, asecond radio 28-1, an (n+1)th radio 28-n, etc.). Each radio 28 mayinclude circuitry that operates on signals at baseband frequencies(e.g., baseband circuitry), signal generator circuitry,modulation/demodulation circuitry (e.g., one or more modems),radio-frequency transceiver circuitry (e.g., radio-frequency transmittercircuitry, radio-frequency receiver circuitry, mixer circuitry fordownconverting radio-frequency signals to baseband frequencies orintermediate frequencies between radio and baseband frequencies and/orfor upconverting signals at baseband or intermediate frequencies toradio-frequencies, etc.), amplifier circuitry (e.g., one or more poweramplifiers and/or one or more low-noise amplifiers (LNAs)),analog-to-digital converter (ADC) circuitry, digital-to-analog converter(DAC) circuitry, control paths, power supply paths, signal paths (e.g.,radio-frequency transmission lines, intermediate frequency transmissionlines, baseband signal lines, etc.), switching circuitry, filtercircuitry, and/or any other circuitry for transmitting and/or receivingradio-frequency signals using antenna(s) 34. The components of eachradio 28 may be mounted onto a respective substrate or integrated into arespective integrated circuit, chip, package, or system-on-chip (SOC).If desired, the components of multiple radios 28 may share a singlesubstrate, integrated circuit, chip, package, or SOC.

Antenna(s) 34 may be formed using any desired antenna structures. Forexample, antenna(s) 34 may include antennas with resonating elementsthat are formed from loop antenna structures, patch antenna structures,inverted-F antenna structures, slot antenna structures, planarinverted-F antenna structures, helical antenna structures, monopoleantennas, dipoles, hybrids of these designs, etc. Filter circuitry,switching circuitry, impedance matching circuitry, and/or other antennatuning components may be adjusted to adjust the frequency response andwireless performance of antenna(s) 34 over time.

Transceiver circuitry in radios 28 may convey radio-frequency signalsusing one or more antennas 34 (e.g., antenna(s) 34 may convey theradio-frequency signals for the transceiver circuitry). The term “conveyradio-frequency signals” as used herein means the transmission and/orreception of the radio-frequency signals (e.g., for performingunidirectional and/or bidirectional wireless communications withexternal wireless communications equipment). Antenna(s) 34 may transmitthe radio-frequency signals by radiating the radio-frequency signalsinto free space (or to free space through intervening device structuressuch as a dielectric cover layer). Antenna(s) 34 may additionally oralternatively receive the radio-frequency signals from free space (e.g.,through intervening devices structures such as a dielectric coverlayer). The transmission and reception of radio-frequency signals byantenna(s) 34 each involve the excitation or resonance of antennacurrents on an antenna resonating element in the antenna by theradio-frequency signals within the frequency band(s) of operation of theantenna.

Each radio 28 may be coupled to one or more antennas 34 over one or moreradio-frequency transmission lines 31. Radio-frequency transmissionlines 31 may include coaxial cables, microstrip transmission lines,stripline transmission lines, edge-coupled microstrip transmissionlines, edge-coupled stripline transmission lines, transmission linesformed from combinations of transmission lines of these types, etc.Radio-frequency transmission lines 31 may be integrated into rigidand/or flexible printed circuit boards if desired. One or moreradio-frequency lines 31 may be shared between radios 28 if desired.Radio-frequency front end (RFFE) modules may be interposed on one ormore radio-frequency transmission lines 31. The radio-frequency frontend modules may include substrates, integrated circuits, chips, orpackages that are separate from radios 28 and may include filtercircuitry, switching circuitry, amplifier circuitry, impedance matchingcircuitry, radio-frequency coupler circuitry, and/or any other desiredradio-frequency circuitry for operating on the radio-frequency signalsconveyed over radio-frequency transmission lines 31.

Radios 28 may use antenna(s) 34 to transmit and/or receiveradio-frequency signals within different frequency bands at radiofrequencies (sometimes referred to herein as communications bands orsimply as a “bands”). The frequency bands handled by radios 28 mayinclude wireless local area network (WLAN) frequency bands (e.g., Wi-Fi®(IEEE 802.11) or other WLAN communications bands) such as a 2.4 GHz WLANband (e.g., from 2400 to 2480 MHz), a 5 GHz WLAN band (e.g., from 5180to 5825 MHz), a Wi-Fi® 6E band (e.g., from 5925-7125 MHz), and/or otherWi-Fi® bands (e.g., from 1875-5160 MHz), wireless personal area network(WPAN) frequency bands such as the 2.4 GHz Bluetooth® band or other WPANcommunications bands, cellular telephone frequency bands (e.g., bandsfrom about 600 MHz to about 5 GHz, 3G bands, 4G LTE bands, 5G NRFrequency Range 1 (FR1) bands below 10 GHz, 5G NR Frequency Range 2(FR2) bands between 20 and 60 GHz, etc.), other centimeter or millimeterwave frequency bands between 10-300 GHz, near-field communications (NFC)frequency bands (e.g., at 13.56 MHz), satellite navigation frequencybands (e.g., a GPS band from 1565 to 1610 MHz, a Global NavigationSatellite System (GLONASS) band, a BeiDou Navigation Satellite System(BDS) band, etc.), ultra-wideband (UWB) frequency bands that operateunder the IEEE 802.15.4 protocol and/or other ultra-widebandcommunications protocols, communications bands under the family of 3GPPwireless communications standards, communications bands under the IEEE802.XX family of standards, and/or any other desired frequency bands ofinterest.

Each radio 28 may transmit and/or receive radio-frequency signalsaccording to a respective radio access technology (RAT) that determinesthe physical connection methodology for the components in thecorresponding radio. One or more radios 28 may implement multiple RATsif desired. As just one an example, the radios 28 in device 10 mayinclude a UWB radio 28-0 for conveying UWB signals using one or moreantennas 34, a Bluetooth (BT) radio 28-1 for conveying BT signals usingone or more antennas 34, a Wi-Fi radio 28-3 for conveying WLAN signalsusing one or more antennas 34, a cellular radio 28-4 for conveyingcellular telephone signals using one or more antennas 34 (e.g., in 4Gfrequency bands, 5G FR1 bands, and/or 5G FR2 bands), an NFC radio 28-5for conveying NFC signals using one or more antennas 34, and a wirelesscharging radio 28-6 for receiving wireless charging signals using one ormore antennas 34 for charging a battery on device 10. This example ismerely illustrative and, in general, radios 28 may include any desiredcombination of radios for covering any desired combination of RATs.

Radios 28 may use antenna(s) 34 to transmit and/or receiveradio-frequency signals to convey wireless communications data betweendevice 10 and external wireless communications equipment (e.g., one ormore other devices such as device 10, a wireless access point or basestation, etc.). Wireless communications data may be conveyed by radios28 bidirectionally or unidirectionally. The wireless communications datamay, for example, include data that has been encoded into correspondingdata packets such as wireless data associated with a telephone call,streaming media content, internet browsing, wireless data associatedwith software applications running on device 10, email messages, etc.Radios 28 may also use antenna(s) 34 to perform spatial rangingoperations (e.g., for identifying a distance between device 10 and anexternal object such as external object 8). Radios 28 that performspatial ranging operations may include radar circuitry if desired (e.g.,frequency modulated continuous wave (FMCW) radar circuitry, OFDM radarcircuitry, FSCW radar circuitry, a phase coded radar circuitry, othertypes of radar circuitry).

During radio-frequency signal transmission, some of the radio-frequencysignals transmitted by antenna(s) 34 may be incident upon externalobjects such as external object 8. External object 8 may be, forexample, the body of the user of device 10 or another human or animal.In these scenarios, the amount of radio-frequency energy exposure atexternal object 8 may be characterized by one or more radio-frequency(RF) energy exposure metrics. The RF exposure (RFE) metrics may includespecific absorption rate (SAR) for radio-frequency signals atfrequencies less than 6 GHz (in units of W/kg), maximum permissibleexposure (MPE) for radio-frequency signals at frequencies greater than 6GHz (in units of mW/cm²), and total exposure ratio (TER), which combinesSAR and MPE.

Regulatory requirements often impose limits on the amount of RF energyexposure permissible for external object 8 within the vicinity ofantenna(s) 34 over a specified time period (e.g., an SAR limit and anMPE limit over a corresponding averaging period). Radios 28 that handleradio-frequency signals at frequencies greater than 6 GHz are sometimesreferred to herein as MPE radios 28 because these radios 28 may besubject to MPE limits. Radios 28 that handle radio-frequency signals atfrequencies less than 6 GHz are sometimes referred to herein as SARradios 28 because these radios 28 may be subject to SAR limits. Radios28 that handle signals greater than 6 GHz and signals less than 6 GHz(e.g., a cellular telephone radio 28) are subject to both SAR and MPElimits and are therefore both a SAR radio and an MPE radio.

Wireless circuitry 24 may include RF exposure metric manager 26 forensuring that radios 28 comply with these regulatory requirements. Thecomponents of RF exposure metric manager 26 may be implemented inhardware (e.g., one or more processors, circuit components, logic gates,diodes, transistors, switches, arithmetic logic units (ALUs), registers,application-specific integrated circuits, field-programmable gatearrays, etc.) and/or software on device 10. RF exposure metric manager26 may sometimes be referred to herein as RF exposure manager 26, RFexposure managing engine 26, RF exposure metric management circuitry 26,RF exposure metric management engine 26, or RF exposure metricmanagement processor 26. RF exposure metric manager 26 may be coupled toeach radio 28 over a respective control path 30 (e.g., control path 30-0may couple RF exposure metric manager 26 to radio 28-0, control path30-1 may couple RF exposure metric manager 26 to radio 28-1, controlpath 30-n may couple RF exposure metric manager 26 to radio 28-n, etc.).

RF exposure metric manager 26 may generate RF exposure budgets BGT forradios 28 (e.g., a first RF exposure budget BGT0 for radio 28-0, asecond RF exposure budget BGT1 for radio 28-1, an (n+1)th RF exposurebudget BGTn for radio 28-n, etc.). RF exposure metric manager 26 mayprovide RFE budgets BGT to radios 28 over control paths 30. Each RFEbudget BGT may include a corresponding SAR budget BGT_(SAR) and/or acorresponding MPE budget BGT_(MPE) (e.g., depending on whether the radiosubject to that budget is subject to SAR and/or MPE limits). Each radio28 that is subject to SAR limits may receive a respective SAR budgetBGT_(SAR) and each radio 28 that is subject to MPE limits may receive arespective MPE budget BGT_(MPE) from RF exposure metric manager 26. EachSAR budget BGT_(SAR) may specify the amount of SAR that may be generatedby the corresponding radio 28 in transmitting radio-frequency signalsover the regulatory averaging period while still satisfying the overallSAR regulatory limits. Each MPE budget BGT_(MPE) may specify the amountof MPE that may be generated by the corresponding radio 28 intransmitting radio-frequency signals over the regulatory averagingperiod while still satisfying the overall MPE regulatory limits. Thecircuitry in radios 28 may adjust the maximum transmit (TX) power levelof its transmitted radio-frequency signals (e.g., using a maximum powerreduction (MPR) command, etc.) to ensure that the RF exposure budget BGTfor that radio remains satisfied over the averaging period.

In some scenarios, each radio or RAT in device 10 is assigned a fixedSAR/MPE budget, such that the distribution of the total available RFexposure budget across RATs remains static over time to meet the overallSAR/MPE regulatory limits on the operation of device 10 (e.g., over theaveraging period). In these scenarios, each radio uses look-up tables toderive the maximum transmit power levels allowed for its fixed SAR/MPEbudget and then maintains its transmit power level below that maximumtransmit power level to satisfy the SAR/MPE limits. However, assigningstatic SAR/MPE budgets to the radios in this way without considering theradio needs for the current operating state/environment of device 10results in sub-optimal budget distribution between the radios/RATs. Forexample, the part of the overall RF exposure budget that is not used byone radio cannot be re-assigned to another radio that may urgently needto transmit at a higher power level or increased duty cycle.

In order to mitigate these issues, RF exposure metric manager 26 maydynamically allocate SAR and MPE budgets to radios 28 over time (e.g.,over the averaging period). RF exposure metric manager 26 maydynamically allocate SAR and MPE budgets to radios 28 based on feedbackfrom radios 28. For example, as shown in FIG. 1, each radio 28 may becoupled to RF exposure metric manager 26 over feedback path 32. Eachradio 28 may generate a SAR/MPE report RPT that identifies the amount ofthe assigned SAR and/or MPE budget that was consumed by that radioduring different sub-periods (sometimes referred to herein asinstantaneous periods) of the averaging period. SAR/MPE reports RPT maysometimes also be referred to herein as SAR/MPE feedback reports RPT,feedback reports RPT, SAR/MPE feedback RPT, feedback RPT, SAR/MPEfeedback signals RPT, or feedback signals RPT. Radios 28 may send theSAR/MPE reports RPT to RF exposure metric manager 26 over feedback path32 (e.g., radio 28-0 may send SAR/MPE report RPT0 to RF exposure metricmanager 26, radio 28-1 may send SAR/MPE report RPT1 to RF exposuremetric manager 26, radio 28-n may send SAR/MPE report RPTn to RFexposure metric manager 26, etc.). RF exposure metric manager 26 mayreceive each SAR/MPE report through the active transmission of thereports by radios 28 (e.g., as control signals or other control data) orby querying or retrieving the reports from radios 28 (e.g., bytransmitting control signals or commands to the radios instructing theradios to transmit the corresponding report to RF exposure metricmanager 26). RF exposure metric manager 26 may generate updated RFexposure budgets BGT for radios 28 based on the received SAR/MPE reportsRPT and based on the current or expected communication needs of device10 to ensure that radios 28 can continue to transmit radio-frequencysignals to meet the active and dynamic needs of device 10 while stillsatisfying the SAR and MPE limits imposed on device 10 over theaveraging period. In this way, RF exposure metric manager 26 may assignSAR/MPE budgets across RATs while ensuring an SAR/MPE compliant overallRF exposure across the RATs.

As an example, RF exposure metric manager 26 may include an RF exposurerule database, a total RF exposure calculation engine, and a budgetcalculation and distribution engine. The RF exposure rule database maybe hard-coded or soft-coded into RF exposure metric manager 26 (e.g., instorage circuitry 16 of FIG. 1) and may include a database, data table,or any other desired data structure. The RF exposure rule database maystore RF exposure rules associated with the operation of wirelesscircuitry 24 within different geographic regions. The RF exposure ruledatabase may, for example, store regulatory SAR limits, regulatory MPElimits, and averaging periods T_(AVG) for the SAR limits and MPE limitsfor one or more geographic regions (e.g., countries, continents, states,localities, municipalities, provinces, sovereignties, etc.) that imposeregulatory limits on the amount of RF energy exposure permissible forexternal object 8 within the vicinity of antenna(s) 34. As an example,the RF exposure rule database may store a first SAR limit, a first MPElimit, and a first averaging period T_(AVG) imposed by the regulatoryrequirements of a first country, a second SAR limit, a second MPE limit,and a second averaging period T_(AVG) imposed by the regulatoryrequirements of a second country, etc. The entries of the RF exposurerule database may be stored upon manufacture, assembly, testing, and/orcalibration of device 10 and/or may be updated during the operation ofdevice 10 over time (e.g., periodically or in response to a triggercondition such as a software update or the detection that device 10 hasentered a new country for the first time).

The total RF exposure calculation engine in RF exposure metric manager26 may receive SAR/MPE reports RPT from radios 28 over feedback path 32.Each SAR/MPE report RPT may include a corresponding SAR report and/or acorresponding MPE report. For example, the SAR/MPE report RPT0 producedby radio 28-0 of FIG. 1 may include a first SAR report and a first MPEreport, the SAR/MPE report RPT1 produced by radio 28-1 may include asecond SAR report and a second MPE report, etc. For radios 28 that donot operate at frequencies greater than 6 GHz (e.g., SAR radios 28), theMPE report generated by that radio may be null or empty or that radio 28may omit an MPE report from its SAR/MPE report RPT. Similarly, forradios 28 that do not operate at frequencies less than 6 GHz (e.g., MPEradios 28), the SAR report generated by that radio may be null or emptyor that radio 28 may omit a SAR report from its SAR/MPE report RPT.

The total RF exposure calculation engine may generate (e.g., compute,calculate, identify, produce, etc.) an average consumed SAR value, anaverage consumed MPE value, and a consumed total exposure ratio valuebased on the SAR/MPE reports RPT received over feedback path 32, theaveraging period T_(AVG) received from the RF exposure rule database,and the SAR limit and the MPE limit received from the RF exposure ruledatabase. The RF exposure rule database may identify a particularaveraging period T_(AVG), a particular SAR limit, and a particular MPElimit to send to the total RF exposure calculation engine based on thecurrent geographic location of device 10.

The total RF exposure calculation engine may generate an average SARvalue based on the SAR reports in the SAR/MPE reports RPT received overfeedback path 32. The average SAR value may be indicative of the averageamount of the current SAR budgets consumed by all of the radios 28 inwireless circuitry 24 during the current averaging period T_(AVG).Similarly, the total RF exposure calculation engine may generate anaverage MPE value based on the MPE reports in the SAR/MPE reports RPTreceived over feedback path 32. The average MPE value may be indicativeof the average amount of the current MPE budgets consumed by all of theradios 28 in wireless circuitry 24 during the current averaging periodT_(AVG). The total RF exposure calculation engine may generate a totalexposure ratio value indicative of the combined SAR and MPE consumptionby all of the radios 28 in wireless circuitry 24 during the currentaveraging period T_(AVG).

The budget calculation and distribution engine in RF exposure metricmanager 26 may generate updated RF exposure budgets BGT for each radio28 in wireless circuitry 24 based on the average SAR value, the averageMPE value, the total exposure ratio value, the SAR limit, and the MPElimit. The budget calculation and distribution engine may also generatethe updated RF exposure budgets BGT while taking into account whichradios may or may not need to perform more or less transmission at anygiven time. For example, the budget calculation and distribution enginemay generate updated RF exposure budgets BGT based on SAR/MPEdistribution policies, SAR/MPE radio transmit (TX) activity factors,SAR/MPE radio statuses, and/or SAR/MPE radio usage ratios. The SAR/MPEdistribution policies may identify which SAR radios 28 require SARbudget at a current point in time and which MPE radios 28 require MPEbudget at a current point in time (e.g., because the radios already havea wireless connection established with external communicationequipment). The SAR/MPE radios 28 that are actively communicating withexternal communications equipment and conveying a relatively largeamount of data may, for example, require more SAR/MPE budget and may beallocated more SAR/MPE budget than the SAR/MPE radios 28 that are notactively communicating with the external communications equipment orthat are conveying a relatively low amount of data. The SAR/MPE radiostatuses may identify which SAR/MPE radios 28 are active or in an idleor sleep mode at any given time. SAR/MPE radios 28 that are active may,for example, require more SAR/MPE budget than SAR/MPE radios that areidle, inactive, or asleep. The SAR/MPE radio TX activity factors mayidentify the amount of transmit activity being used or expected to beused by each SAR/MPE radio 28. SAR/MPE radios 28 that have a high amountof actual or expected transmit activity may, for example, require moreSAR/MPE budget than SAR/MPE radios that have a relatively small amountof actual or expected transmit activity. The SAR/MPE radio usage ratiosmay identify how much of past SAR/MPE budgets was actually used by eachSAR/MPE radio 28. A SAR/MPE radio 28 that used all or most of itsallocated SAR/MPE budget during one or more of the previousinstantaneous periods and/or averaging periods may, for example, requiremore SAR/MPE budget during the next instantaneous period than SAR/MPEradios 28 that used relatively little of its SAR/MPE budget during theprevious instantaneous periods. The updated RF exposure budgets BGT mayserve to dynamically adjust the amount of SAR/MPE budget provided toeach radio within the current averaging period T_(AVG) and/or acrossmultiple averaging periods T_(AVG).

The budget calculation and distribution engine may provide each RFexposure budget BGT to the corresponding radio 28 to be subjected tothat RF exposure budget over control paths 30. Each RF exposure budgetBGT may include a corresponding SAR budget BGT_(SAR) and/or acorresponding MPE budget BGT_(MPE). For radios 28 that do not operate atfrequencies greater than 6 GHz (e.g., SAR radios 28), the MPE budgetgenerated for that radio may be null or empty or the budget calculationand distribution engine may omit an MPE budget from the RF exposurebudget for that radio. Similarly, for radios 28 that do not operate atfrequencies less than 6 GHz (e.g., MPE radios 28), the SAR budgetgenerated for that radio may be null or empty or the budget calculationand distribution engine may omit an SAR budget from the RF exposurebudget for that radio.

Radios 28 may use the updated RF exposure budgets produced by the budgetcalculation and distribution engine to transmit radio-frequency signals.The radios may produce SAR/MPE reports RPT associated with thetransmission of radio-frequency signals using the updated RF exposurebudgets. This process may iterate to continue to update the RF exposurebudgets provided to each radio over time, thereby allowing RF exposuremetric manager 26 to dynamically adjust the amount of SAR and MPE budgetprovided to each radio based on feedback from previous transmissions bythe radio, the SAR and MPE limits imposed by the correspondingregulatory body, and the current or future communications needs ofdevice 10.

The example of FIG. 1 is merely illustrative. While control circuitry 14is shown separately from wireless circuitry 24 in the example of FIG. 1for the sake of clarity, wireless circuitry 24 may include processingcircuitry (e.g., one or more processors) that forms a part of processingcircuitry 18 and/or storage circuitry that forms a part of storagecircuitry 16 of control circuitry 14 (e.g., portions of controlcircuitry 14 may be implemented on wireless circuitry 24). As anexample, control circuitry 14 may include baseband circuitry (e.g., oneor more baseband processors) or other control circuitry that forms partof radios 28. The baseband circuitry may, for example, access acommunication protocol stack on control circuitry 14 (e.g., storagecircuitry 20) to: perform user plane functions at a PHY layer, MAClayer, RLC layer, PDCP layer, SDAP layer, and/or PDU layer, and/or toperform control plane functions at the PHY layer, MAC layer, RLC layer,PDCP layer, RRC, layer, and/or non-access stratum layer. If desired, thePHY layer operations may additionally or alternatively be performed byradio-frequency (RF) interface circuitry in wireless circuitry 24. Inaddition, wireless circuitry 24 may include any desired number ofantennas 34. Some or all of the antennas 34 in wireless circuitry 24 maybe arranged into one or more phased antenna arrays (e.g., for conveyingradio-frequency signals over a steerable signal beam). If desired,antenna(s) 34 may be operated using a multiple-input and multiple-output(MIMO) scheme and/or using a carrier aggregation (CA) scheme.

In some scenarios, each radio 28 maintains RFE compliance within its RFEbudget BGT by applying a fixed maximum transmit (TX) power limit or byapplying TX power averaging. TX power averaging keeps the average(conducted) TX power below a certain TX power limit P_(LIMIT) (e.g.,where TX power can occasionally exceed P_(LIMIT) but the average TXpower does not exceed P_(LIMIT) over the averaging period T_(AVG)).However, TX power limits are radio technology and frequency banddependent. As such, an average TX power cannot be maintained duringtransitions between radios and frequency bands. In addition, the TXpower limit depends on device position (e.g., if the device is at auser's head, on a body, relatively far from the user, etc.). As such,the average TX power cannot be maintained when the device positionchanges over time.

In order to mitigate these issues while ensuring RFE compliance, eachradio 28 may perform time-domain averaging of RFE metrics such as SARand MPE rather than averaging the conducted TX power on antenna(s) 34.For example, the SAR/MPE budget for radio 28 may be converted into acorresponding target TX power and target duty cycle to be used foruplink (UL) transmission. The radio may measure instantaneous TX powerand duty cycle and may convert the TX power back to consumedinstantaneous SAR/MPE values. The instantaneous SAR/MPE values may beused for time domain averaging of SAR/MPE. The radio may calculate theremaining SAR/MPE budget based on the averaged SAR/MPE and may adjust TXpower level and duty cycle to maintain the averaged SAR/MPE within theprovided overall budget.

FIG. 2 is a circuit block diagram showing how a given radio 28 mayperform time-domain averaging of SAR/MPE for maintaining RFE compliancewithout performing time-domain averaging of conducted TX power. As shownin FIG. 2, radio 28 may include RFE budget conversion circuitry 36,transmitter 40, antenna coefficient database 55, instantaneous RFEcalculation circuitry 48, RFE averaging circuitry 60, and remaining RFEbudget calculation circuitry 66. RFE budget conversion circuitry 36 maysometimes be referred to herein as RFE budget converter 36 or RFE budgetconversion engine 36. Transmitter 40 may sometimes be referred to hereinas transmitter circuitry 40. Instantaneous RFE calculation circuitry 48may sometimes be referred to herein as instantaneous RFE calculator 48or instantaneous RFE calculation engine 48. RFE averaging circuitry 60may sometimes be referred to herein as RFE averager 60 or RFE averagingengine 60. Remaining RFE budget calculation circuitry 66 may sometimesbe referred to herein as remaining RFE budget calculator 66 or remainingRFE budget calculation engine 66. The components of RFE budgetconversion circuitry 36, instantaneous RFE calculation circuitry 48, RFEaveraging circuitry 60, and remaining RFE budget calculation circuitry66 may be implemented in hardware (e.g., using one or more processors,circuit components, logic gates, diodes, transistors, switches,arithmetic logic units (ALUs), registers, application-specificintegrated circuits, field-programmable gate arrays, etc.) and/orsoftware on device 10. Antenna coefficient database 55 may include adatabase, data tables, or any other desired data structure (e.g., onstorage circuitry 16 of FIG. 1). If desired, RFE budget conversioncircuitry 36, instantaneous RFE calculation circuitry 48, RFE averagingcircuitry 60, remaining RFE budget calculation circuitry 66, and/orantenna coefficient database 55 may be implemented on baseband circuitry(e.g., a baseband processor) in radio 28.

RFE budget conversion circuitry 36 may have an input coupled to controlpaths 30. RFE budget conversion circuitry 36 may have an output coupledto transmitter 40 over control path 38. Transmitter 40 may have anoutput coupled to a corresponding antenna 34 over radio-frequencytransmission line 31. Transmitter 40 may receive transmit data TXDATover data path 42 (e.g., from an applications processor on controlcircuitry 14, from baseband circuitry or a baseband processor on radio28, etc.). Transmit data TXDAT may include application data, text data,message data, web data, voice data, video data, or any other desireddata for transmission to external wireless communications equipment(e.g., within the data payload of data packets transmitted bytransmitter 40). Transmitter 40 may include upconverter (e.g., mixer)circuitry, clocking circuitry, voltage-controlled oscillator circuitry,modulator circuitry, synthesizer circuitry, signal generator circuitry,analog-to-digital converter (ADC) circuitry, filter circuitry, switchingcircuitry, amplifier circuitry (e.g., one or more power amplifiers),and/or any other desired circuitry for transmitting radio-frequencysignals over antenna 34 (e.g., radio-frequency signals that includetransmit data TXDAT).

Transmitter 40 may be coupled to antenna coefficient database 55 overcontrol path 50. Transmitter 40 may be coupled to instantaneous RFEcalculation circuitry 48 over control path 46. Instantaneous RFEcalculation circuitry 48 may have a first input coupled to antennacoefficient database 55 over control path 52 and may have a second inputcoupled to transmitter 40 over control path 46. Instantaneous RFEcalculation circuitry 48 may have an output coupled to RFE averagingcircuitry 60 over control path 58. RFE averaging circuitry 60 may havean output coupled to remaining RFE budget calculation circuitry 66 overcontrol path 62 (e.g., instantaneous RFE calculation circuitry 48 may becoupled in series between transmitter 40 and RFE averaging circuitry 60and RFE averaging circuitry 60 may be coupled in series betweeninstantaneous RFE calculation circuitry 48 and remaining RFE budgetcalculation circuitry 66). Remaining RFE budget calculation circuitry 66may have a first input coupled to RFE averaging circuitry 60 overcontrol path 62 and may have a second input coupled to control paths 30.Remaining RFE budget calculation circuitry 66 may have an output coupledto RFE budget conversion circuitry 36 over control path 64. RFE budgetconversion circuitry 36 may also have an input coupled to antennacoefficient database 55 over control path 54.

Antenna coefficient database 55 may store one or more antennacoefficients C. Antenna coefficients C may map conducted TX power to RFEmetrics such as SAR/MPE produced by each of the antennas 34 on device 10under a variety of operating conditions. There may be different antennacoefficients C for different antennas 34, different radio accesstechnologies, different frequency bands, duty cycles, and/or differentdevice positions. Antenna coefficients C may be specific for the designof device 10 and may be derived from laboratory measurements duringdevice design, manufacture, assembly, calibration, and/or testing priorto storage in antenna coefficient database 55. Antenna coefficients Cmay, for example, be calculated from the measured ratio betweenconducted TX power and the SAR/MPE caused by the transmission for eachantenna 34 under different radio access technologies, frequency bands,duty cycles, and/or device positions. As an example, antenna coefficientdatabase 55 may store a first antenna coefficient C that corresponds totransmission by a first antenna 34 using a first frequency band andfirst duty cycle when the device is held in a first position (e.g., upto a user's head), a second antenna coefficient C that corresponds totransmission by the first antenna 34 using the first frequency band andthe first duty cycle when the device is held in a second position (e.g.,on a different portion of the user's body), a third antenna coefficientC that corresponds to transmission by the first antenna 34 using asecond frequency band and the first duty cycle when the device is heldin the first position, a third antenna coefficient C that corresponds totransmission by a second antenna 34 using the second frequency band andthe first duty cycle when the device is held in the second position, afourth antenna coefficient C that corresponds to transmission by thefirst antenna using the second frequency band and a second duty cyclewhen the device is held in the first position, etc. If desired, antennacoefficient database 55 may be updated over time.

Antenna coefficient database 55 may provide the applicable antennacoefficient C for any given transmission period to RFE budget conversioncircuitry 36 over control path 54 and to instantaneous RFE calculationcircuitry 48 over control path 52. If desired, transmitter 40 mayprovide transmission information to antenna coefficient database 55 overcontrol path 50 (or to a memory controller or other controller thatreads antenna coefficient values C from antenna coefficient database55). The transmission information may include information identifyingwhich of the antennas 34 on device 10 is being used by transmitter 40for transmission (e.g., the active antenna), information identifying thefrequency band BND for transmission, and information identifying theduty cycle DC used for the transmission. Antenna coefficient database 55may also receive sensor data SENS over control path 56. Sensor data SENSmay be produced by one or more sensors in input/output devices 22 (FIG.1). Sensor data SENS may, for example, be indicative of whether device10 is being held up to a user's head, on a different portion of theuser's body, away from the user, etc. Antenna coefficient database 55may provide the applicable antenna coefficient C (e.g., the storedantenna coefficient C that maps conducted TX power to SAR/MPE producedby the active antenna 34 during transmission by transmitter 40 usingduty cycle DC in frequency band BND when device 10 is being held in theposition identified by sensor data SENS) to RFE budget conversioncircuitry 36 over control path 54 and to instantaneous RFE calculationcircuitry 48 over control path 52.

RFE budget conversion circuitry 36 and remaining RFE budget calculationcircuitry 66 may receive the RFE budget BGT assigned to radio 28 by RFexposure metric manager 26 (FIG. 1) over control paths 30. RFE budgetBGT may include SAR budget BGT_(SAR) and/or MPE budget BGT_(MPE). Anexample in which radio 28 is both a SAR radio and an MPE radio (e.g., inwhich radio 28 is a cellular radio that transmits signals at frequenciesgreater than 6 GHz and less than 6 GHz) is described herein for thepurpose of illustration. However, if desired, radio 28 may only transmitradio-frequency signals at frequencies less than 6 GHz (in which caseradio 28 need only receive SAR budget BGT_(SAR)) or may only transmitradio-frequency signals at frequencies greater than 6 GHz (in which caseradio 28 need only receive MPE budget BGT_(MPE)). In examples whereradio 28 only transmits radio-frequency signals at frequencies less than6 GHz, the operations of radio 28 described herein as being performedfor both SAR and MPE compliance may only be performed for SARcompliance. In examples where radio 28 only transmits radio-frequencysignals at frequencies greater than 6 GHz, the operations of radio 28described herein as being performed for both SAR and MPE compliance mayonly be performed for MPE compliance.

Radio 28 may transmit radio-frequency signals during the regulatoryaveraging period T_(AVG). Averaging period T_(AVG) is determined by theregulatory body governing the current location of device 10 and isstored in the RF exposure rule database on RF exposure metric manager 26of FIG. 1. Averaging period T_(AVG) may sometimes also be referred to asaveraging window T_(AVG). Averaging period T_(AVG) may be on the orderof a few seconds, 1 second, 4 seconds, 5 seconds, 10-60 seconds, 5-20seconds, 5-60 seconds, 60 seconds, 30 seconds, greater than 60 seconds,etc. Each averaging period T_(AVG) may be divided into a series ofinstantaneous periods (sometimes referred to herein as sub-windows orsubperiods of averaging period T_(AVG)). While referred to herein as“instantaneous” periods, the instantaneous periods have a finiteduration that is less than the duration of averaging period T_(AVG).Each instantaneous period may be, for example, 1 second, 100 ms, between100 ms and 1 second, between 10 ms and 1 second, less than 100 ms, 10ms, between 1 and 100 ms, between 5 ms and 20 ms, between 1 ms and 100ms, etc. The duration of the instantaneous period may be configurable(adjustable) if desired. For example, RF exposure metric manager 26(FIG. 1) may adjust the duration of the instantaneous period to scaleaccording to the applicable use case.

At the beginning of a given averaging period T_(AVG) (e.g., during thefirst instantaneous period of averaging period T_(AVG)), RFE budgetconversion circuitry 36 may generate a maximum transmit power levelPMAX_(SAR) based on SAR budget BGT_(SAR) and the current antennacoefficient(s) C received from antenna coefficient database 55. RFEbudget conversion circuitry 36 may additionally or alternativelygenerate a maximum transmit power level PMAX_(MPE) based on MPE budgetBGT_(MPE) and the current antenna coefficient(s) C received from antennacoefficient database 55. RFE budget conversion circuitry 36 may generate(e.g., compute, produce, calculate, derive, deduce, estimate, identify,etc.) maximum transmit power level PMAX_(SAR) according to equation 1and/or may generate maximum transmit power level PMAX_(MPE) according toequation 2, for example.

$\begin{matrix}{{PMAX}_{SAR} = \frac{C1}{BGT_{SAR}}} & (1) \\{{PMAX}_{MPE} = \frac{C2}{BGT_{MPE}}} & (2)\end{matrix}$

In equation 1, C1 is the current antenna coefficient C provided byantenna coefficient database 55 and corresponding to transmission bytransmitter 40 in a frequency band BND at frequencies less than 6 GHzusing a selected antenna 34. In equation 2, C2 is the current antennacoefficient C provided by antenna coefficient database 55 andcorresponding to transmission by transmitter 40 in a frequency band BNDat frequencies greater than 6 GHz using the selected antenna 34. RFEbudget conversion circuitry 36 may include one or more dividers forgenerating PMAX_(SAR) and PMAX_(MPE), for example. Maximum transmitpower levels PMAX_(SAR) and/or PMAX_(MPE) may be scaled down for dutycycles DC that are less than 100% (e.g., where antenna coefficients C1and/or C2 correspond to the duty cycle less than 100% that is used). RFEbudget conversion circuitry 36 may pass maximum transmit power levelsPMAX_(SAR) and/or PMAX_(MPE) to transmitter 40 over control path 38.

Transmitter 40 may transmit radio-frequency signals (e.g.,radio-frequency signals that include transmit data TXDAT) over antenna34 subject or pursuant to (e.g., based on) maximum transmit power levelsPMAX_(SAR) and/or PMAX_(MPE) (e.g., during the current instantaneousperiod). Transmitter 40 may identify (e.g., generate, produced,retrieve, compute, calculate, etc.) the amount of conducted TX powertransmitted by transmitter 40 and antenna 34 at frequencies less than 6GHz (P0_(<6)) and/or the amount of conducted TX power transmitted bytransmitter 40 and antenna 34 at frequencies greater than 6 GHz(P0_(>6)). Transmitter 40 may identify conducted TX powers P0_(<6) andP0_(>6) using its known transmit power, the duration of the currenttransmit instance (e.g., within the instantaneous period)T_(TRANSMIT_INST), and the applicable antenna coefficient(s) C.Additionally or alternatively, transmitter 40 may include powermeasurement circuitry that actively measures conducted TX powers P0_(<6)and/or P0_(>6) from the transmitted radio-frequency signals.T_(TRANSMIT_INST) may be equal to the duration of one radio time slotused by transmitter 40, as an example. Transmitter 40 may passT_(TRANSMIT_INST), P0_(<6), and P0_(>6) to instantaneous RFE calculationcircuitry 48 over control path 46.

Instantaneous RFE calculation circuitry 48 may map the conducted TXpower P0_(<6) onto the underlying SAR produced by transmitter 40 duringthe current instantaneous period (sometimes referred to herein asinstantaneous SAR) and/or may map the conducted TX power P0_(>6) ontothe underlying MPE produced by transmitter 40 during the currentinstantaneous period (sometimes referred to herein as instantaneousMPE). In other words, instantaneous RFE calculation circuitry 48 maygenerate (e.g., compute, calculate, produce, derive, deduce, estimate,identify, etc.) an instantaneous SAR value SAR_(INST) based on conductedTX power P0_(<6), the current antenna coefficient C1 received fromantenna coefficient database 55, and T_(TRANSMIT_INST) and/or maygenerate an instantaneous MPE value MPE_(INST) based on conducted TXpower P0_(>6), the current antenna coefficient C2 received from antennacoefficient database 55, and T_(TRANSMIT_INST). For example,instantaneous RFE calculation circuitry 48 may generate instantaneousSAR value SAR_(INST) according to equation 3 and/or may generateinstantaneous MPE value MPE_(INST) according to equation 4.SAR_(INST) =C1*P0_(<6) *T _(TRANSMIT_INST)  (3)MPE_(INST) =C2*P0_(>6) *T _(TRANSMIT_INST)  (4)

Instantaneous RFE calculation circuitry 48 may include one or moremultipliers for generating instantaneous SAR value SAR_(INST) and/orinstantaneous MPE value MPE_(INST), for example. Conducted TX powersP0_(<6) and P0_(>6) may be in units of mW, for example. Antennacoefficient C1 may map conducted power in units of mW to SAR in units ofW/kg. Instantaneous SAR value SAR_(INST) is therefore in units of Ws/kgor J/kg. Antenna coefficient C2 may map conducted power in units of mWto MPE in units of mW/cm². Instantaneous MPE value MPE_(INST) istherefore in units of mWs/cm² or mJ/cm². As an example, when transmitter40 has an output power P_(OUT) of 18 dBm and produces a conducted powerP0_(<6)=63 mW when antenna coefficient C1=1/63 g, instantaneous RFEcalculation circuitry 48 may generate a SAR value equal to 6 mw*(1/63g)=1 W/kg. Instantaneous RFE calculation circuitry 48 may multiply thisSAR value by T_(TRANSMIT_INST) to obtain instantaneous SAR valueSAR_(INST). RFE calculation circuitry 48 may provide instantaneous SARvalue SAR_(INST) and/or instantaneous MPE value MPE_(INST) to RFEaveraging circuitry 60 over control path 58.

RFE averaging circuitry 60 may store the instantaneous SAR valuesSAR_(INST) and/or the instantaneous MPE values MPE_(INST) generated byinstantaneous RFE calculation circuitry 48 for each instantaneous periodof the current averaging period T_(AVG). RFE averaging circuitry 60 mayaverage the instantaneous SAR value SAR_(INST) generated byinstantaneous RFE calculation circuitry 48 during the currentinstantaneous period with each of the instantaneous SAR valuesSAR_(INST) generated by instantaneous RFE calculation circuitry 48during each of the previous instantaneous periods of the currentaveraging period T_(AVG) to produce a consumed (average) SAR valueSAR_(CONSUMED). Additionally or alternatively, RFE averaging circuitry60 may average the instantaneous MPE value MPE_(INST) generated byinstantaneous RFE calculation circuitry 48 during the currentinstantaneous period with each of the instantaneous MPE valuesMPE_(INST) generated by instantaneous RFE calculation circuitry 48during each of the previous instantaneous periods of the currentaveraging period T_(AVG) to produce a consumed (average) MPE valueMPE_(CONSUMED). For example, RFE averaging circuitry 60 may generate(e.g., produce, calculate, identify, compute, deduce, estimate, etc.)consumed SAR value SAR_(CONSUMED) according to equation 5 and/or maygenerate consumed MPE value MPE_(CONSUMED) according to equation 6.

$\begin{matrix}{{SAR}_{CONSUMED} = \frac{\sum\limits_{i = 1}^{n}{SAR}_{INST}}{T_{ELAPSED}}} & (5) \\{{MPE}_{CONSUMED} = \frac{\sum\limits_{i = 1}^{n}{MPE}_{INST}}{T_{ELAPSED}}} & (6)\end{matrix}$

In equations 5 and 6, “i” is an index, “n” is the number ofinstantaneous periods in the current averaging period T_(AVG) that havealready elapsed (e.g., the number of instantaneous SAR values SAR_(INST)already gathered for the current averaging period T_(AVG)), andT_(ELAPSED) is the portion of averaging period T_(AVG) that has alreadyelapsed (e.g., n times the duration of the instantaneous periods inaveraging period T_(AVG)). RFE averaging circuitry 60 may include one ormore dividers and one or more adders for generating consumed SAR valueSAR_(CONSUMED) and/or consumed MPE value MPE_(CONSUMED), for example.RFE averaging circuitry 60 may pass consumed SAR value SAR_(CONSUMED)and/or consumed MPE value MPE_(CONSUMED) to remaining RFE budgetcalculation circuitry 66 over control path 62.

Remaining RFE budget calculation circuitry 66 may generate (e.g.,produce, deduce, determine, identify, estimate, identify, calculate,compute, etc.) a remaining SAR budget SAR_(REM) based on the consumedSAR value SAR_(CONSUMED) generated by RFE averaging circuitry 60 and theSAR budget BGT_(SAR) received from RF exposure metric manager 26 overcontrol paths 30. Additionally or alternatively, remaining RFE budgetcalculation circuitry 66 may generate a remaining MPE budget MPE_(REM)based on the consumed MPE value MPE_(CONSUMED) generated by RFEaveraging circuitry 60 and the MPE budget BGT_(MPE) received from RFexposure metric manager 26 over control paths 30. For example, remainingRFE budget calculation circuitry 66 may generate remaining SAR budgetSAR_(REM) according to equation 7 and/or may generate remaining MPEbudget MPE_(REM) according to equation 8.

$\begin{matrix}{{SAR_{REM}} = \frac{{{BGT}_{SAR}*T_{AVG}} - {{SA}_{CONSUMED}*T_{ELAPSED}}}{T_{REM}}} & (7) \\{{{MP}E_{REM}} = \frac{{{BGT}_{MPE}*T_{AVG}} - {{MPE}_{CONSUMED}*T_{ELAPSED}}}{T_{REM}}} & (8)\end{matrix}$

In equations 7 and 8, T_(REM) is portion of averaging period T_(AVG)that has not yet elapsed (e.g., where T_(REM)=T_(AVG)−T_(ELAPSED)).Remaining RFE budget calculation circuitry 66 may include one or moredividers, one or more multipliers, and one or more adders for generatingremaining SAR budget SAR_(REM) and/or remaining MPE budget MPE_(REM),for example. Remaining RFE budget calculation circuitry 66 may provideremaining SAR budget SAR_(REM) and/or remaining MPE budget MPE_(REM) toRFE budget conversion circuitry 36 over control path 64.

Consider an example in which the SAR consumed within the first threeseconds of a four-second averaging period T_(AVG) exceeds a SAR budgetBGT_(SAR) of 1 W/kg. In this example, for the remaining 1 second, only areduced budget of (1 W/kg*4 s−1.2 W/kg*3 s)/(1 s)=0.4 W/kg is available(e.g., as remaining SAR budget SAR_(REM)) to keep SAR averaged over thefour-second averaging period within SAR budget BGT_(SAR). In anotherexample where the SAR consumed in the first three seconds of afour-second averaging period T_(AVG) is less than a SAR budget BGT_(SAR)of 1 W/kg, a remaining SAR budget SAR_(REM) equal to (1 W/kg*4 s−0.7W/kg*3 s)/(1 s)=1.9 W/kg is available. Even when using this higher SARduring the remaining one second of the averaging period, the total SARaveraged over the four second averaging period remains within SAR budgetBGT_(SAR).

After the first instantaneous period of the current averaging periodT_(AVG), RFE budget conversion circuitry 36 may generate maximumtransmit power level PLIMIT_(SAR) based on remaining SAR budgetSAR_(REM) and antenna coefficient C1 (e.g., by replacing SAR budgetBGT_(SAR) with remaining SAR budget SAR_(REM) in equation 1).Additionally or alternatively, RFE budget conversion circuitry 36 maygenerate maximum transmit power level PLIMIT_(MPE) based on remainingMPE budget MPE_(REM) and antenna coefficient C2 (e.g., by replacing MPEbudget BGT_(MPE) with remaining MPE budget MPE_(REM) in equation 2). RFEbudget conversion circuitry 36 may provide maximum transmit power levelPLIMIT_(SAR) and/or maximum transmit power level PLIMIT_(MPE) totransmitter 40 over control path 38. For the instantaneous periods afterthe first instantaneous period of the current averaging period,transmitter 40 may transmit radio-frequency signals subject or pursuantto (e.g., based on) maximum transmit power level PLIMIT_(SAR) (ratherthan maximum transmit power level PMAX_(SAR)) for radio-frequencysignals at frequencies less than 6 GHz and may transmit radio-frequencysignals subject or pursuant to (e.g., based on) maximum transmit powerlevel PLIMIT_(MPE) (rather than maximum transmit power level PMAX_(MPE))for radio-frequency signals at frequencies greater than 6 GHz.

In this way, radio 28 may perform time-domain averaging of SAR and/orMPE (rather than time-domain averaging conducted TX power) toiteratively adjust the remaining SAR and/or MPE budgets for the radio toensure RFE compliance over the averaging period. Time-domain averagingSAR and/or MPE in this way may also lead to improved and simplifiedhandling of transient scenarios relative to time-averaging conducted TXpower. For example, averaged SAR/MPE may be maintained as the activefrequency band BND or radio access technology changes over time. Merelyaveraging conducted TX power cannot maintain a time-domain average ofSAR/MPE because the mapping between SAR/MPE and allowed maximum transmitpower level is dependent upon frequency band and radio accesstechnology. Averaged SAR/MPE may similarly be maintained as changes inRF exposure conditions occur over time, such as when the device movesfrom away from a user's body to on the user's body to near the user'shead. Time-domain averaging SAR and/or MPE in this way may also allowfor budget sharing across radio access technologies. For example,SAR/MPE budget may be shared between cellular, WLAN, Bluetooth, UWB,and/or other radio access technologies because averaged SAR/MPE valuesare of the same quantity, whereas averaged conducted TX power is stilldependent upon radio access technology, frequency band, and activeantenna.

FIG. 3 is a circuit block diagram of RFE budget conversion circuitry 36in one illustrative example. As shown in FIG. 3, RFE budget conversioncircuitry 36 may include divider circuitry such as a first divider 67and a second divider 68. Dividers 67 and 68 may each have a first inputcoupled to control paths 30 and 64. Divider 67 may have a second inputthat receives antenna coefficient C1 from antenna coefficient database55 (e.g., over control path 54 of FIG. 2). Divider 68 may have a secondinput that receives antenna coefficient C2 from antenna coefficientdatabase 55. Divider 67 or 68 may be omitted in examples where radio 28only transmits radio-frequency signals at less than 6 GHz or onlytransmits radio-frequency signals at greater than 6 GHz.

During a first instantaneous period of a current averaging periodT_(AVG), divider 67 may divide the SAR budget BGT_(SAR) received overcontrol paths 30 by antenna coefficient C1 to generate (e.g., produce,compute, calculate, etc.) maximum transmit power level PMAX_(SAR) (e.g.,according to equation 1). During the first instantaneous period of thecurrent averaging period T_(AVG), divider 68 may divide the MPE budgetBGT_(MPE) received over control paths 30 by antenna coefficient C2 togenerate maximum transmit power level PMAX_(MPE) (e.g., according toequation 2). During subsequent instantaneous periods of the currentaveraging period T_(AVG), divider 67 may divide the remaining SAR budgetSAR_(REM) received over control path 64 by antenna coefficient C1 togenerate maximum transmit power level PLIMIT_(SAR) and/or divider 68 maydivide the remaining MPE budget MPE_(REM) received over control path 64by antenna coefficient C2 to generate maximum transmit power levelPLIMIT_(MPE). Divider 67 may output maximum transmit power levelsPMAX_(SAR) and PLIMIT_(SAR) and divider 68 may output maximum transmitpower levels PMAX_(MPE) and PLIMIT_(MPE) onto control path 38. Ifdesired, the same divider may be used to produce the maximum transmitpower levels for both MPE and SAR.

FIG. 4 is a circuit block diagram of instantaneous RFE calculationcircuitry 48 in one illustrative example. As shown in FIG. 4,instantaneous RFE calculation circuitry 48 may include multipliercircuitry such as a first multiplier 70 and a second multiplier 72.Multipliers 70 and 72 may each have first and second inputs coupled tocontrol path 46. Multiplier 70 may have a third input that receivesantenna coefficient C1 from antenna coefficient database 55 (e.g., overcontrol path 52 of FIG. 2). Multiplier 72 may have a third input thatreceives antenna coefficient C2 from antenna coefficient database 55.Multiplier 70 or 72 may be omitted in examples where radio 28 onlytransmits radio-frequency signals at less than 6 GHz or only transmitsradio-frequency signals at greater than 6 GHz.

During each instantaneous period of the current averaging periodT_(AVG), multiplier 70 may multiply the conducted transmit power P0_(<6)received from transmitter 40 by the time T_(TRANSMIT_INST) received fromtransmitter 40 and by the antenna coefficient C1 received from antennacoefficient database 55 to produce generate (e.g., produce, compute,calculate, etc.) instantaneous SAR value SAR_(INST). Additionally oralternatively, multiplier 72 may multiply the conducted transmit powerP0_(>6) received from transmitter 40 by the time T_(TRANSMIT_INST)received from transmitter 40 and by the antenna coefficient C2 receivedfrom antenna coefficient database 55 to produce generate instantaneousMPE value MPE_(INST). Multiplier 70 may output instantaneous SAR valueSAR_(INST) and multiplier 72 may output instantaneous MPE valueMPE_(INST) onto control path 58. If desired, the same multiplier may beused to produce both instantaneous SAR value SAR_(INST) andinstantaneous MPE value MPE_(INST).

FIG. 5 is a flow chart of illustrative operations that may be performedby a given radio 28 on device 10 to maintain RFE compliance bytime-averaging SAR and/or MPE (e.g., using the components of FIGS. 2-4).At operation 80, RFE budget conversion circuitry 36 and remaining RFEbudget calculation circuitry 66 on radio 28 may receive SAR budgetBGT_(SAR) and/or MPE budget BGT_(MPE) from RF exposure metric manager 26(FIG. 1). Radio 28 may also receive information identifying the currentaveraging period T_(AVG) from RF exposure metric manager 26.

At operation 82, during a first instantaneous period of the currentaveraging period T_(AVG), RFE budget conversion circuitry 82 maygenerate maximum transmit power level PMAX_(SAR) based on SAR budgetBGT_(SAR) and antenna coefficient C1 (e.g., according to equation 1).Additionally or alternatively, RFE budget conversion circuitry 82 maygenerate maximum transmit power level PMAX_(MPE) based on MPE budgetBGT_(MPE) and antenna coefficient C2 (e.g., according to equation 2).Antenna coefficient database 55 may provide antenna coefficients C(e.g., antenna coefficient C1 and/or C2) to instantaneous RFEcalculation circuitry 48 and RFE budget conversion circuitry 36 thatcorrespond to the active antenna 34, the duty cycle DC for transmission,the frequency band BND and radio access technology for transmission, andthe current position or orientation of device 10 (e.g., as identified bysensor data SENS of FIG. 2), for example. RFE budget conversioncircuitry 82 may provide maximum transmit power level PMAX_(SAR) and/ormaximum transmit power level PMAX_(MPE) to transmitter 40.

At operation 84, during the first instantaneous period of the currentaveraging period T_(AVG), transmitter 40 may transmit radio-frequencysignals subject to maximum transmit power levels PMAX_(SAR) and/orPMAX_(MPE). Transmitter 40 may transmit the radio-frequency signals infrequency band BND, using the duty cycle DC, and using the activeantenna 34 corresponding to the antenna coefficients C1 and/or C2received by RFE budget conversion circuitry 36.

At operation 86, transmitter 40 may identify the conducted TX powersP0_(<6) and/or P0_(>6) produced by transmitter 40 and antenna 34 intransmitting the radio-frequency signals during the currentinstantaneous period of the current averaging period T_(AVG) (e.g., asproduced while performing operation 84 during a first iteration of theoperations of FIG. 5). Transmitter 40 may also identify the timeT_(TRANSMIT_INST) in which the radio-frequency signals were transmittedfor the current instantaneous period. Transmitter 40 may provideT_(TRANSMIT_INST), P0_(<6), and/or P0_(>6) to instantaneous RFEcalculation circuitry 48.

At operation 88, instantaneous RFE calculation circuitry 48 may generateinstantaneous SAR value SAR_(INST) based on conducted TX power P0_(<6),T_(TRANSMIT_INST), and antenna coefficient C1 (e.g., according toequation 3). Additionally or alternatively, instantaneous RFEcalculation circuitry 48 may generate instantaneous MPE value MPE_(INST)based on conducted TX power P0_(>6), T_(TRANSMIT_INST), and antennacoefficient C2 (e.g., according to equation 4). Instantaneous RFEcalculation circuitry 48 may store the instantaneous SAR valueSAR_(INST) and/or instantaneous MPE value MPE_(INST) (e.g., at RFEaveraging circuitry 60) for the current instantaneous period of thecurrent averaging period T_(AVG) for use during subsequent processing.In this way, the instantaneous SAR values SAR_(INST) and/or theinstantaneous MPE values MPE_(INST) may be accumulated and stored foraveraging by RFE averaging circuitry 60 over the current averagingperiod T_(AVG).

At operation 90, RFE averaging circuitry 90 may generate consumed SARvalue SAR_(CONSUMED) by averaging the instantaneous SAR value SAR_(INST)produced for the current instantaneous period (e.g., for the currentiteration of operations 86-94 of FIG. 5) with each of the instantaneousSAR values SAR_(INST) that have already been generated and stored duringprevious instantaneous periods of the current averaging period T_(AVG)(e.g., according to equation 5). Additionally or alternatively, RFEaveraging circuitry 90 may generate consumed MPE value MPE_(CONSUMED) byaveraging the instantaneous MPE value MPE_(INST) produced for thecurrent instantaneous period (e.g., for the current iteration ofoperations 86-94 of FIG. 5) with each of the instantaneous MPE valuesMPE_(INST) that have already been generated and stored during previousinstantaneous periods of the current averaging period T_(AVG) (e.g.,according to equation 6). RFE averaging circuitry 60 may provideconsumed SAR value SAR_(CONSUMED) and/or consumed MPE valueMPE_(CONSUMED) to remaining RFE budget calculation circuitry 66.

At operation 92, remaining RFE budget calculation circuitry 66 maygenerate remaining SAR budget SAR_(REM) based on SAR budget BGT_(SAR),consumed SAR value SAR_(CONSUMED), the duration of averaging periodT_(AVG), the elapsed portion T_(ELAPSED) of the averaging period, andthe remaining portion T_(REM) of the averaging period (e.g., accordingto equation 7). Additionally or alternatively, remaining RFE budgetcalculation circuitry 66 may generate remaining MPE budget MPE_(REM)based on MPE budget BGT_(MPE), consumed MPE value MPE_(CONSUMED), theduration of averaging period T_(AVG), the elapsed portion T_(ELAPSED) ofthe averaging period, and the remaining portion T_(REM) of the averagingperiod (e.g., according to equation 8). Remaining RFE budget calculationcircuitry 66 may provide remaining SAR budget SAR_(REM) and/or remainingMPE budget MPE_(REM) to RFE budget conversion circuitry 36.

At operation 94, RFE budget conversion circuitry 36 may generate maximumpower limit PLIMIT_(SAR) for the next instantaneous period of thecurrent averaging period T_(AVG) based on remaining SAR budget SAR_(REM)and antenna coefficient C1 (e.g., by replacing SAR budget BGT_(SAR) inequation 1 with remaining SAR budget SAR_(REM)). Additionally oralternatively, RFE budget conversion circuitry 36 may generate maximumpower limit PLIMIT_(MPE) for the next instantaneous period of thecurrent averaging period T_(AVG) based on remaining MPE budget MPE_(REM)and antenna coefficient C2 (e.g., by replacing MPE budget BGT_(MPE) inequation 2 with remaining MPE budget MPE_(REM)).

If instantaneous periods remain in the current averaging period T_(AVG)(e.g., if T_(REM) is greater than the duration of one instantaneousperiod), processing may proceed to operation 98 via path 96 to incrementthe current instantaneous period of the current averaging periodT_(AVG). Processing may then proceed to operation 100. At operation 100,transmitter 40 may transmit radio-frequency signals during the current(e.g., incremented) instantaneous period subject to maximum transmitpower levels PLIMIT_(SAR) and/or PLIMIT_(MPE). Processing may then loopback to operation 86 via path 102 to allow radio 28 to continue toperform time-domain averaging of SAR and/or MPE for updating the maximumtransmit power levels PLIMIT_(SAR) and/or PLIMIT_(MPE) used fortransmission during the remainder of the current averaging periodT_(AVG). Once no instantaneous periods remain in the current averagingperiod (e.g., when T_(REM) is less than the duration of an instantaneousperiod), processing may proceed from operation 94 to operation 106 viapath 104 to increment the current averaging period T_(AVG). Processingmay then loop back to operation 82 via path 108 to perform time-domainaveraging of SAR/MPE for ensuring RFE compliance over the current(incremented) averaging period T_(AVG).

The example of FIG. 5 is merely illustrative. Two or more of theoperations of FIG. 5 may be performed concurrently or in other orders.If desired, RFE budget conversion circuitry 36 may omit generation ofmaximum transmit power levels PLIMIT_(SAR) and PLIMIT_(MPE) when thereare no instantaneous periods remaining in the current averaging period.Radio 28 may change the duty cycle DC, frequency band BND, and/or theactive antenna 34 during or between iterations of the operations of FIG.5. Antenna coefficient database 55 may update the antenna coefficientsC1/C2 used during one or more of these operations as necessary toaccount for changes in duty cycle DC, frequency band BND, and/or activeantenna 34. Device 10 may also change positions or orientations duringor between iterations of the operations of FIG. 5 (e.g., in a mannerthat affects SAR/MPE produced by radio 28). Antenna coefficient database55 may update the antenna coefficients C1/C2 used during one or more ofthese operations as necessary to account for changes in device positionor orientation. RF exposure metric manager 26 may also change the SARbudget BGT_(SAR) and/or the MPE budget BGT_(MPE) for radio 28 during orbetween iterations of the operations of FIG. 5. This may ensure thatradio 28 maintains RFE compliance even when duty cycle DC, frequencyband BND, the active antenna 34, or the device position changes overtime.

To further illustrate some of the advantages of maintaining RFEcompliance via time-averaging SAR/MPE rather than conducted TX power,consider an example in which device 10 transitions from a first positionadjacent to a user's head to a second position on the user's body butaway from the user's head. In this example, device 10 may be subject toan averaging period T_(AVG) of 60 seconds, may spend the first thirtyseconds of the averaging period in the first position, and may spend thelast thirty seconds of the averaging period in the second position. Forthe sake of illustration, radio 28 may receive a SAR budget BGT_(SAR) of2 W/kg for the averaging period (e.g., at operation 80 of FIG. 5).

Plot 112 of FIG. 6 illustrates this example when device 10 performstime-averaging of conducted TX power rather than time-averaging SAR forRFE compliance. Curve 116 of plot 112 illustrates the maximum transmitpower level that would be imposed in this scenario. At 30 seconds, themaximum transmit power level reduces from 18 dBm (63 mW) to 12 dBm (15.8mW) due to the change in device position. Curve 118 of plot 112illustrates the instantaneous transmit power level of transmitter 40. Asshown by curve 118, the instantaneous transmit power of transmitter 40is forced to remain below the maximum transmit power level associatedwith curve 116 (e.g., 12 dBm) for the entire remainder of the averagingperiod (e.g., from 30 to 60 seconds) to maintain SAR compliance. Thismay limit the radio-frequency performance (e.g., efficiency andthroughput) of transmitter 40 in communicating with externalcommunications equipment.

Plot 114 of FIG. 6 illustrates the same example but where device 10performs time-averaging of SAR rather than time-averaging of conductedTX power. Curve 118 plots the applicable SAR limit. Curve 120 plotsinstantaneous transmit power level of transmitter 40. Curve 122 plotsthe time-averaged total SAR (e.g., consumed SAR value SAR_(CONSUMED))over the current averaging period. During the first thirty seconds ofthe averaging period, one or more sensors on device 10 may identify thatdevice 10 is in the first position (e.g., adjacent to a user's head).Antenna coefficient database 55 may, for example, identify an antennacoefficient C1 that is equal to 1/63 when device 10 is in the firstposition (e.g., for the corresponding active antenna, frequency bandBND, and duty cycle DC). Radio 28 may, for example, transmit with aconstant 15 dBm during the first thirty seconds of the averaging period.In this example, the average SAR consumed is equal to 0.5 W/kg (e.g.,where 15 dBm=31.62 mW and 31.62 mW*(1/63)=0.5 W/kg).

After 30 seconds of the averaging period have elapsed, the sensors ondevice 10 may identify that device 10 is in the second position (e.g.,on the user's body but away from the user's head). Antenna coefficientdatabase 55 may, for example, identify an antenna coefficient C1 that isequal to 1/15.8 when device 10 is in the second position (e.g., for thecorresponding active antenna, frequency band BND, and duty cycle DC).The available SAR budget remaining for seconds 30-60 is equal to 1.5W/kg (e.g., since 0.5 W/kg of the 2 W/kg SAR budget BGT_(SAR) wereconsumed during seconds 0-30). This is equivalent to a transmit powerlimit of 13.7 dBm (e.g., where 1.5 W/kg/(1/15.8)=23.7 mW or 13.7 dBm).As such, radio 28 may transmit with a maximum transmit power level of13.7 dBm during seconds 30-60 instead of transmitting at only 12 dBm(e.g., as shown in plot 112). This allows the transmit power level toexceed the limit associated with curve 116 by margin 124, therebymaximizing the radio-frequency performance (e.g., throughput andefficiency) of radio 28 relative to scenarios where a strict TX powerlimit is applied or where time-domain averaging of conducted TX power isperformed instead of time-domain averaging of SAR. At the same time, thetime-averaged total SAR associated with curve 122 remains below SARlimit 118, thereby ensuring that radio 28 satisfies regulatory limits onSAR. Time-domain averaging of MPE may be performed similarly when thetransmitted radio-frequency signals are greater than 6 GHz.

Consider another example in which radio 28 is a cellular radio and inwhich device 10 transitions from performing only cellular transmissionswith radio 28 from seconds 0-30 of the averaging period to performingboth cellular transmissions with radio 28 and Wi-Fi transmissions (e.g.,using an additional radio) during seconds 30-60 of the averaging period.In this example, radio 28 may receive a SAR budget BGT_(SAR) of 1 W/kgfor seconds 0-30 of the averaging period and may receive a SAR budgetBGT_(SAR) of 0.5 W/kg for seconds 30-60 of the averaging period (e.g.,because RF exposure metric manager 26 of FIG. 1 allocates some of theoverall SAR budget for device 10 to the Wi-Fi radio).

FIG. 7 illustrates this example when device 10 performs time-averagingof SAR rather than time-averaging of conducted TX power. Curve 126 plotsthe applicable transmit power limit, which reduces from 18 dBm to 15 dBmin response to the activation of the Wi-Fi radio. Curve 128 plots theapplicable SAR limit. Curve 130 plots instantaneous transmit power levelof transmitter 40. Curve 132 plots time-averaged total SAR. Radio 28 mayhave the same antenna coefficient C1 during both seconds 0-30 andseconds 30-60 (e.g., because activation of the Wi-Fi radio does notaffect the conducted power of the antenna 34 used for cellularcommunications). Radio 28 may, for example, transmit with a constant 15dBm during the first thirty seconds of the averaging period. In thisexample, the average SAR consumed is equal to 0.5 W/kg (e.g., where 15dBm=31.62 mW and 31.62 mW*(1/63)=0.5 W/kg). Since the SAR budget for thefirst 30 seconds is 1 W/kg in this example, there is 0.5 W/kg of SARbudget that goes unused from seconds 0-30. Radio 28 therefore has anexpanded SAR budget of 1.0 W/kg for seconds 30-60 (e.g., the 0.5 W/kgassigned in the SAR budget SAR_(BGT) plus the unused 0.5 W/kg from thefirst 30 seconds). This is equivalent to a transmit power limit of 18dBm (e.g., where 1 W/kg/(1/63)=63 mW or 18 dBm). As such, radio 28 maytransmit with a maximum transmit power level of 18 dBm during seconds30-60 instead of transmitting at only 15 dBm or lower, as would be thecase if time-domain averaging of conducted power were used. This therebyserves to maximize the radio-frequency performance (e.g., throughput andefficiency) of radio 28 relative to scenarios where time-domainaveraging of conducted TX power is performed instead of time-domainaveraging of SAR. At the same time, the time-averaged total SARassociated with curve 132 remains below SAR limit 128, thereby ensuringthat radio 28 satisfies regulatory limits on SAR. Time-domain averagingof MPE may be performed similarly when the transmitted radio-frequencysignals are greater than 6 GHz. The examples of FIGS. 6 and 7 are merelyillustrative.

Device 10 may gather and/or use personally identifiable information. Itis well understood that the use of personally identifiable informationshould follow privacy policies and practices that are generallyrecognized as meeting or exceeding industry or governmental requirementsfor maintaining the privacy of users. In particular, personallyidentifiable information data should be managed and handled so as tominimize risks of unintentional or unauthorized access or use, and thenature of authorized use should be clearly indicated to users.

The methods and operations described above in connection with FIGS. 1-7(e.g., the operations of FIG. 5) may be performed by the components ofdevice 10 using software, firmware, and/or hardware (e.g., dedicatedcircuitry or hardware). Software code for performing these operationsmay be stored on non-transitory computer readable storage media (e.g.,tangible computer readable storage media) stored on one or more of thecomponents of device 10 (e.g., storage circuitry 16 of FIG. 1). Thesoftware code may sometimes be referred to as software, data,instructions, program instructions, or code. The non-transitory computerreadable storage media may include drives, non-volatile memory such asnon-volatile random-access memory (NVRAM), removable flash drives orother removable media, other types of random-access memory, etc.Software stored on the non-transitory computer readable storage mediamay be executed by processing circuitry on one or more of the componentsof device 10 (e.g., processing circuitry 18 of FIG. 1, etc.). Theprocessing circuitry may include microprocessors, central processingunits (CPUs), application-specific integrated circuits with processingcircuitry, or other processing circuitry. The components of FIGS. 1-4may be implemented using hardware (e.g., circuit components, digitallogic gates, one or more processors, etc.) and/or using software whereapplicable. While databases are sometimes described herein as providingdata to other components (see, e.g., antenna coefficient database 55 ofFIG. 2), one or more processors, memory controllers, or other componentsmay actively access the databases, may retrieve the stored data from thedatabase, and may pass the retrieved data to the other components forcorresponding processing. The regulatory SAR limit, MPE limit, andaveraging times described herein need not be imposed by a government orregulatory body and may additionally or alternatively be imposed by anetwork operator, base station, or access point of a wireless network inwhich device 10 operates, by device 10 itself, by the manufacturer ordesigner of some or all of device 10, by wireless industry standards,protocols, or practices, by software running on device 10, etc.

The foregoing is merely illustrative and various modifications can bemade to the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. An electronic device comprising: an antenna; aradio communicably coupled to the antenna; and one or more processorsconfigured to generate a first maximum transmit power level based on aradio-frequency exposure (RFE) budget assigned to the radio and anantenna coefficient associated with the antenna, generate aninstantaneous RFE metric value based on the antenna coefficient and aconducted transmit power of the antenna during the first subperiod,generate a consumed RFE metric value by averaging the instantaneous RFEmetric value with at least one additional instantaneous RFE metric valuegenerated by the one or more processors for one or more subperiods ofthe averaging period that are prior to the first subperiod, generate aremaining RFE budget for the averaging period based on the consumed RFEmetric value and the RFE budget, and generate a second maximum transmitpower level based on the remaining RFE budget and the antennacoefficient, the radio being configured to transmit firstradio-frequency signals using the antenna during a first subperiod of anaveraging period while subject to the first maximum transmit powerlevel, and transmit second radio-frequency signals using the antennaduring a second subperiod of the averaging period subsequent to thefirst subperiod while subject to the second maximum transmit powerlevel.
 2. The electronic device of claim 1, wherein the firstradio-frequency signals and the second radio-frequency signals are at afrequency greater than 6 GHz, the RFE budget comprises a maximumpermissible exposure (MPE) budget, the instantaneous RFE metric valuecomprises an instantaneous MPE value, the consumed RFE metric valuecomprises a consumed MPE value, and the remaining RFE budget comprises aremaining MPE budget.
 3. The electronic device of claim 1, wherein thefirst radio-frequency signals and the second radio-frequency signals areat a frequency less than 6 GHz, the RFE budget comprises a specificabsorption rate (SAR) budget, the instantaneous RFE metric valuecomprises an instantaneous SAR value, the consumed RFE metric valuecomprises a consumed SAR value, and the remaining RFE budget comprises aremaining SAR budget.
 4. The electronic device of claim 1, furthercomprising: an antenna coefficient database that stores a set of antennacoefficients that are each associated with a respective combination oftransmit frequency, duty cycle, active antenna, and device position,wherein the set of antenna coefficients includes the antennacoefficient.
 5. The electronic device of claim 1, wherein the one ormore processors is configured to generate the first maximum transmitpower level by dividing the RFE budget by the antenna coefficient. 6.The electronic device of claim 5, wherein the one or more processors isconfigured to generate the second maximum transmit power level bydividing the remaining RFE budget by the antenna coefficient.
 7. Theelectronic device of claim 1, wherein the one or more processors isconfigured to generate the instantaneous RFE metric value by multiplyingthe conducted transmit power by the antenna coefficient and by aduration within the first subperiod during which the radio transmittedthe first radio-frequency signals.
 8. The electronic device of claim 1,wherein the one or more processors is configured to generate theremaining RFE budget based on a duration of the averaging period, aduration of the averaging period that has already elapsed, and aduration of the averaging period that has yet to elapse, wherein theremaining RFE budget is directly proportional to the duration of theaveraging period and the RFE budget, and wherein the remaining RFEbudget is inversely proportional to the duration of the averaging periodthat has yet to elapse.
 9. The electronic device of claim 1, wherein theantenna coefficient includes a ratio of conducted transmit power to theRFE metric value given a frequency of the first radio-frequency signalsand the second radio-frequency signals, a duty cycle of the firstradio-frequency signals and the second radio-frequency signals, and acurrent orientation of the electronic device.
 10. The electronic deviceof claim 1, further comprising: an additional radio configured totransmit radio-frequency signals using a different radio accesstechnology than the radio, wherein the one or more processors isconfigured to reduce the RFE budget for the radio when the additionalradio is active.
 11. A method of operating an electronic device havingone or more antennas configured to handle one or more radio-frequencypolarizations, a radio subject to a limit on radio-frequency exposure(RFE) over an averaging period, and one or more processors, the methodcomprising: with the radio, transmitting first radio-frequency signalsusing the one or more antennas during a first subperiod of the averagingperiod while subject to a first maximum transmit power level; with theone or more processors, generating an instantaneous RFE metric valuebased on an antenna coefficient associated with the one or more antennasand based on a conducted transmit power of the one or more antennasduring the first subperiod; with the one or more processors, generatinga consumed RFE metric value by averaging the instantaneous RFE metricvalue with at least one additional instantaneous RFE metric valuegenerated for one or more subperiods of the averaging period that areprior to the first subperiod; with the one or more processors,generating a remaining RFE budget for the averaging period based on theconsumed RFE metric value; with the one or more processors, generating asecond maximum transmit power level based on the remaining RFE budget;and with the radio, transmitting second radio-frequency signals using atleast one of the one or more antennas during a second subperiod of theaveraging period while subject to the second maximum transmit powerlevel, the second subperiod being subsequent to the first subperiod. 12.The method of claim 11, further comprising: with the one or moreprocessors, generating the first maximum transmit power level based onthe antenna coefficient and an RFE budget assigned to the radio.
 13. Themethod of claim 12, wherein generating the second maximum transmit powerlevel comprises generating the second maximum transmit power level basedon the antenna coefficient.
 14. The method of claim 11, whereingenerating the second maximum transmit power level comprises generatingthe second maximum transmit power level based on the antennacoefficient.
 15. The method of claim 11 wherein the firstradio-frequency signals and the second radio-frequency signals are at afrequency greater than 6 GHz, the instantaneous RFE metric valuecomprises an instantaneous maximum permissible exposure (MPE) value, theconsumed RFE metric value comprises a consumed MPE value, and theremaining RFE budget comprises a remaining MPE budget.
 16. The method ofclaim 11, wherein the first radio-frequency signals and the secondradio-frequency signals are at a frequency less than 6 GHz, theinstantaneous RFE metric value comprises an instantaneous SAR value, theconsumed RFE metric value comprises a consumed SAR value, and theremaining RFE budget comprises a remaining SAR budget.
 17. The method ofclaim 11, wherein generating the first maximum transmit power levelcomprises dividing an RFE budget assigned to the radio by the antennacoefficient, generating the second maximum transmit power levelcomprises by dividing the remaining RFE budget by the antennacoefficient, and generating the instantaneous RFE metric value comprisesmultiplying the conducted transmit power by the antenna coefficient. 18.The method of claim 17, wherein generating the remaining RFE budgetcomprises generating the remaining RFE budget based on the RFE budget, aduration of the averaging period, a duration of the averaging periodthat has already elapsed, and a duration of the averaging period thathas yet to elapse.
 19. An electronic device comprising: one or moreantennas; a radio communicably coupled to the one or more antennas andsubject to a limit on maximum permissible exposure (MPE) over anaveraging period; and one or more processors configured to convert anMPE budget assigned to the radio into a first maximum transmit powerlevel, generate an instantaneous MPE value based on a conducted transmitpower of the one or more antennas during the subperiod, generate aconsumed MPE value by averaging the instantaneous MPE value with atleast one prior instantaneous MPE metric value generated during theaveraging period, generate a remaining MPE budget for the averagingperiod based on the consumed MPE value and the MPE budget, and generatea second maximum transmit power level based on the remaining MPE budget,the radio being configured to transmit first radio-frequency signals ata frequency greater than 6 GHz using at least one of the one or moreantennas during a subperiod of the averaging period and while subject tothe first maximum transmit power level, and transmit secondradio-frequency signals at the frequency greater than 6 GHz using atleast one of the one or more antennas during a subsequent subperiod ofthe averaging period and while subject to the second maximum transmitpower level.
 20. The electronic device of claim 19, wherein the one ormore processors is configured to convert the MPE budget into the firstmaximum transmit power level based on an antenna coefficient associatedwith transmission by the antenna at the frequency greater than 6 GHz,the one or more processors is configured to generate the second maximumtransmit power level based on the antenna coefficient, and the one ormore processors is configured to generate the instantaneous MPE valuebased on the antenna coefficient.